4g61t.org

Specializing in the 3g CSM
It is currently Thu Mar 28, 2024 1:32 pm

All times are UTC-05:00




Post new topic  Reply to topic  [ 46 posts ]  Go to page 1 2 3 4 Next
Author Message
PostPosted: Tue Sep 02, 2003 6:21 am 
Offline
CSM Expert
User avatar

Joined: Tue Aug 05, 2003 7:10 am
Posts: 2686
Location: Germany
Hi!

Recently so many of us tried to elaborate some differences between the 8 valve and the 12 valve 4G15 heads, either to find out if they're non-interference or how retarding the cam will give more horses or doing a swap.

How about a joint effort in covering all those differences?
I.e. it's known the 8v head is non-interference, while it is unknown if the 12v is. This may be important when retarding the cam timing.
The (German) 8v engine have a CR of 9.4, the (German) 12v have 9.2 but yet higher torque and more power. Is the CR reduced due to head construction or in the pistons?

Common guys let the research begin!

_________________
Got rabies?


Top
   
 Post subject:
PostPosted: Tue Sep 02, 2003 5:58 pm 
Offline
Member
User avatar

Joined: Wed Jan 15, 2003 6:33 pm
Posts: 191
Location: England
This is what I've picked up, so it may not be accurate.

12 valves have flat top pistons, 8 valves have little dent bits for the valves.

12 valve carb and injection heads are identical in design. Not sure about 8 valve, never seen an injection 8 valve.

Putting an 8 valve head onto a 12 valve block with its flat top pistons is supposed to bump up the CR nicely.

I have these figures for the injection 8 valves and 12 valves (also have carb info if interestted)

12 Valve 91PS (6000rpm) 121.6Nm (3000rpm)
8 Valve 82 PS (5500rpm) 123.56Nm (3000rpm)


Top
   
 Post subject:
PostPosted: Tue Sep 02, 2003 10:15 pm 
Offline
CSM Expert
User avatar

Joined: Sun Jan 06, 2002 7:00 pm
Posts: 1792
Location: Perth, Australia
The 8v EFI head is very different to the 8v carby head. The EFI head has larger inlet ports spaced differently although the exhaust ports are the same. Plus the EFI head has no provision for a mechanical fuel pump although there is a still a lobe on the camshaft for it.

The 8v carby 4G15 block uses flat-top pistons and the head has hemispherical combustion chambers. The EFI 8v 4G15 block has dished pistons, the head combustion chambers are smaller and kidney shaped - the combination of which maintains the same CR as the carby engine.


Top
   
 Post subject:
PostPosted: Wed Sep 03, 2003 5:09 am 
Offline
CSM Expert
User avatar

Joined: Tue Aug 05, 2003 7:10 am
Posts: 2686
Location: Germany
Thanks guys! I'm gonna type up my comprehensive list about that now.... I'll post it when it is all typed in.

_________________
Got rabies?


Top
   
 Post subject:
PostPosted: Wed Sep 03, 2003 5:52 am 
Offline
CSM Expert
User avatar

Joined: Tue Aug 05, 2003 7:10 am
Posts: 2686
Location: Germany
EDIT: Thanks to Jason, that stuff is now here:
http://www.4g61t.com/howtos/4g15.html

I think I will post more
Code:
code
here when I have actualized everything. Right now I cut it out to save some space on Jason's HDD.

_________________
Got rabies?


Last edited by The Ethereal on Wed Sep 03, 2003 12:19 pm, edited 1 time in total.

Top
   
 Post subject:
PostPosted: Wed Sep 03, 2003 5:57 am 
Offline
Member
User avatar

Joined: Wed Jan 15, 2003 6:33 pm
Posts: 191
Location: England
I own a 12 valve carb, its got a lot more power than that, but maybe its because mine is a Proton engine (not available in USA). I thought it was identical to the mitsubishi 12 valve carb.


Top
   
 Post subject:
PostPosted: Wed Sep 03, 2003 6:07 am 
Offline
CSM Expert
User avatar

Joined: Tue Aug 05, 2003 7:10 am
Posts: 2686
Location: Germany
Most of this info is from a German book about European engines. That's what is making things really weird sometimes. This is also the cause why I wanted to include RON and MON ratings, as RON is used in Europe and MON in America.
How much power and torque does your Proton engine have? DIN HP/SAE HP/kW?
I'm afraid we will only find out the differences in international 4G15s here, nothing more...

_________________
Got rabies?


Top
   
 Post subject:
PostPosted: Wed Sep 03, 2003 7:09 am 
http://www.4g61t.com/howtos/4g15.html


Top
   
 Post subject:
PostPosted: Wed Sep 03, 2003 9:32 am 
Offline
Member
User avatar

Joined: Wed Jan 15, 2003 6:33 pm
Posts: 191
Location: England
From the back of my Proton Manual for 12v carb. What carb did mitsubishi use? Mine is an Aisan variable venturi (listed on www.nardek.com.au)

Mine has CR of 9.2:1 64Kw@6000rpm and 118Nm@4000rpm.

I'm quite sure this engine is identical to a Mitsubishi, everything is stamped with mitsubishi part numbers.


Top
   
 Post subject:
PostPosted: Wed Sep 03, 2003 12:16 pm 
Offline
CSM Expert
User avatar

Joined: Tue Aug 05, 2003 7:10 am
Posts: 2686
Location: Germany
Strange. The torque indicates a carbed 4G15. But the rest doesn't fit. How can one get more power with less compression? 64 kW equals 87 HP DIN or 86 HP SAE. Maybe they use a different carb. AFAIK Mitsu used Mikuni Solex carbs, type 32-20 I think. Or was that the FBC used in G15B? :-?

_________________
Got rabies?


Top
   
 Post subject:
PostPosted: Wed Sep 03, 2003 12:27 pm 
Offline
CSM Expert
User avatar

Joined: Tue Aug 05, 2003 7:10 am
Posts: 2686
Location: Germany
Quote:
Putting an 8 valve head onto a 12 valve block with its flat top pistons is supposed to bump up the CR nicely.
Will this really fit w/o damaging anything? How much would CR increase? If this will work out we had an instant upgrade for all 12 valve engines. 8) And never worrying about a broken timing belt again... :)

_________________
Got rabies?


Top
   
 Post subject: 8vs12 valve head
PostPosted: Thu Sep 04, 2003 2:30 pm 
Offline
Spends Too Much Time Under The Hood
User avatar

Joined: Fri Jul 25, 2003 4:57 pm
Posts: 212
Location: Albany, OR
i have two spair 8 valve heads and one 12 valve. I notice that the oil galleys are different and so are the water jackets. You can see the difference if you compare the head gaskets. If for some reason it does work you would have to use the 8 valve intake manifold which means no TB upgrade off the 1.8 and the TPS sensor is different between the two intakes also. However you can swap the sensors by doing a few things. Swap the shaft from your 12 valve TB into the TB on the 8 valve. Putting the TB back together can be a pain in the @$$ but it works. I'm currently working on an adapter plate for an 8 valve intake manifold so that you can do the 1.8 TB upgrade.


'89 Colt
1.5 8 valve
port & polish
8mil excel wires
custom cold air intake


Top
   
 Post subject:
PostPosted: Thu Sep 04, 2003 3:25 pm 
Offline
CSM Expert
User avatar

Joined: Tue Aug 05, 2003 7:10 am
Posts: 2686
Location: Germany
Hey thanks for the info!

Guys please be patient, I'll update that list very soon.

_________________
Got rabies?


Top
   
 Post subject:
PostPosted: Thu Sep 04, 2003 3:59 pm 
Offline
CSM Expert
User avatar

Joined: Tue Aug 05, 2003 7:10 am
Posts: 2686
Location: Germany
Just a short thought: when putting a 8V head on a 12V block, CR increases. When doing vice versa, will CR drop enough to bolt on a turbo and run behind-kicking high boost?
8)

_________________
Got rabies?


Top
   
 Post subject:
PostPosted: Sun Sep 07, 2003 4:48 pm 
Offline
Spends Too Much Time Under The Hood
User avatar

Joined: Sat May 31, 2003 6:22 pm
Posts: 248
Location: Manitoba Canada eh?
Last night I did my valve lash on my engine, im curious, on the intake rockers there is the normal sized valve, but there is a smaller valve. What the h*ll are those for? Im guessin I have a 12v head :-?


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 46 posts ]  Go to page 1 2 3 4 Next

All times are UTC-05:00


Who is online

Users browsing this forum: No registered users and 15 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Limited